Immune Responses to Vaccinations: Gut Microbiota’s Crucial Role

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Immune-Responses-to-Vaccinations--Gut-Microbiotas-Crucial-Role#Vaccines are a highly effective way to prevent infectious diseases as well as reducing the need for #antibiotics and therefore antibiotic resistance. However, #immune responses to vaccinations vary hugely between different individuals and populations. Researchers from Flinders University, South Australia, and Stamford University, USA, have now concluded that the composition and function of an individual’s #gut #microbiota is a driving force in affecting responses to vaccination. The review published in Nature Reviews Immunology, showed how microbiota-targeted interventions could help infants and other at risks group receive the full benefit of effective vaccines.


Vaccines induce B and T cells, which fight bacteria and viruses by producing #antibodies. Both B and T cell responses to vaccinations are highly variable with those living in low-income and middle-income countries (#LMICs) particularly likely to have poorer vaccine #immunogenicity than those in high-income countries (#HICs). A recent meta-analysis of all randomised controlled trials of the Rotarix orally administered vaccine found that whilst its efficacy was 98% after 2 weeks and 94% after 12 months in HICs, it was only 66% and 44%, respectively, in LMICs. Age and immune status before immunisation are also a key factor, with vaccine efficacy estimated to be 70-90% in younger adults, compared to 30-50% in those over 65 years of age.  The published review assessed evidence from clinical cohort studies, interventional studies and animal models that all suggested that the gut microbiota, which is itself highly variable between individuals throughout their lives as well as across different populations, plays a vital role in modulating vaccine immunogenicity.


Increasing evidence was shown to suggest that the gut microbiota is a clear, targetable factor, that is influencing the baseline immune status as well as the response to vaccination. Interventions to modulate the gut bacteria are readily available and cost-effective, including diet, #prebiotics and #probiotics. The research group also reviewed studies that clearly indicated how antibiotic treatment changed the gut microbiota, which can induce major changes in the #metabolome, altering inflammatory responses and impairing antibody responses to vaccination. The team used germ-free mice, or mice with no microbiome, to assess which bacteria are best at supporting immune responses and found strong evidence to show that there is a “potential ‘window of opportunity’ in early life, during which the microbiota may have a more marked influence on immune responses to vaccination”.


There are clearly a broad range of factors altering vaccine efficacy in individuals, and the issue has now been given vast global importance as a result of the COVID-19 pandemic. More research is needed, and is being carried out, to better understand how the microbiota regulates vaccine responses, but there is clearly “the potential of microbiota-targeted interventions to optimize vaccine effectiveness”.


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